1. Field of the Invention
The present invention relates to a method for removal of fine-grained sediments from flowing or stationary water bodies, in particular of such sediments containing noxious materials and organic components, which are dug up or dredged at their deposition place.
2. Brief Description of the Background of the Invention Including Prior Art
Based on the lowering of the speed of flow of the water there are generated deposits of drifts, boulders, and sediments in rivers and lakes. The deposits interfere with shipping and decrease the storage volume of catch basins, storage basins and reservoirs. In addition, the sediments can substantially interfere with the water quality based on anaerobic decomposition and whirling up. In case of flooding or high water the deposits diminish the flow cross-section in addition such that the large amounts of water cannot be removed rapidly and safely.
Therefor, it is unavoidable to continuously remove the sediments at the location of their formation. It is known for this purpose to dredge the sediments from flowing or stationary waters with corresponding provisions and then to carry them off. It has been common practice to redeposit the sediments near the banks or to employ them for the filling of natural or artificial hollow spaces. Fine-grained sediments, in particular sludge or mud like sediments with high parts in organic components have been used mostly in agricultural methods and are distributed over the fields according to their exact situation.
Based on absorption or chemical bonding large enrichments of organic and inorganic materials can be found in particular in fine-grained sediments which result in that fine-grained, mud-containing sediments have to be deposited in special depositories after partial dewatering in order to keep the environmental loading within reasonable limits.
A particular problem is posed by the presence of heavy metals such as for example cadmium, the health hazard of which has been proven by enrichment in the food component chain. Based on the noxious materials occurring in the sediments special depositories with particular safety provisions such as for example sealing of foundations and bases have to be provided, where it becomes more and more difficult to find suitable locations based on the large area of land used, in particular in heavy settled regions. Despite expensive provisions it is not possible to prevent that the noxious materials washed out by seeping waters pass (in favorable situations via a purification plant) in part back into the bodies of water. Based on the difficulty of locating a suitable site the special depositories are in general disposed far removed from the location of the removal of the sediments such that considerable distances of transportation have to be overcome. Besides the high expenditures for such transports, the transports in themselves are cause of considerable environmental loading.
The removal of sediments from bodies of water is becoming more and more a problem based on the amounts of sediment generated. For example the river Neckar fed from areas of the Black Forest requires the removal of about two million cubic meters to be dredged and removed and this amount inceases each year by 100,000 cubic meters. However, space for depositing the sediments in depositories is only to a limited volume available.